The Anatomy of an Erection

The Anatomy of an Erection
By Diana Rodriguez | Medically reviewed by Pat F. Bass III, MD, MPH

You might not think twice about the process by which a penis becomes erect ... until you have trouble having an erection or achieving orgasm.

Most of the time, and for most men, erections http://www.dreddyclinic.com/forum/viewtopic.php?f=31&t=6148 come naturally and with little or no effort. But a number of physical and emotional factors are involved in the process of getting and maintaining an erect penis long enough to achieve satisfaction for you and your partner during sexual intercourse. When one or more of these processes aren’t working, the result can be erectile dysfunction (ED)http://www.dreddyclinic.com/findinformation/ee/erectiledysfunction.php.

Anatomy of the Erect Penis

The penis has three main structures: the corpora cavernosa, the corpus spongiosum, and the tunica albuginea. The corpora cavernosa, which is filled with sponge-like tissue, extends the entire length of the penis. The tunica albuginea is the membrane that covers and protects the corpora cavernosa. The corpus spongiosum, in the middle of the penis, houses the urethra, the opening at the end of the penis through which a man urinates and ejaculates. There is also a network of tissues, muscles, arteries, and veins running through the penis, which allows it to fill with blood and stiffen for an erection.
A man achieves an erect penis from stimulation, such as touching or rubbing the penis, or seeing or thinking about something sexually stimulating and exciting. When stimulation occurs, the brain takes over and works with the nerve endings in the penis. The brain and nerves send messages to the penis to relax, resulting in increased blood flow to the veins and arteries in the penis.
The blood fills the penis, leading to pressure that is contained and supported by the tunica albuginea. Blood entering the penis is essentially locked in by the supporting tissues and membranes, which allows the pressure to be maintained, creating and holding an erection. The testicles also release the hormone testosterone, which play a role in determining when an erection happens and how firm it is.
An erection goes away when the penile muscles tighten up and stop blood from flowing into the penis. This usually happens after orgasm or once the stimulation is no longer present. Read more